The lengths, LLL mm, of precision-machined alloy rods are modeled by a normal distribution with mean 24.0 mm24.0\text{ mm}24.0 mm and standard deviation 0.5 mm0.5\text{ mm}0.5 mm.
Find P(L>25.1)P(L > 25.1)P(L>25.1).
Find, to one decimal place, the value of kkk such that P(L<k)=3P(L>k)P(L < k) = 3 P(L > k)P(L<k)=3P(L>k).
Write down the name given to the value of kkk.
For a different grade of rod, the lengths are normally distributed with mean 30.0 mm30.0\text{ mm}30.0 mm.
Given that the 90th percentile for this grade of rod is 31.922 mm31.922\text{ mm}31.922 mm,
find the standard deviation of the length of this grade of rod.
Practise Edexcel A Level Maths Finding Probabilities for Normal Distributions with exam-style questions for A Level Maths. 80 questions, matched to the Edexcel A Level Maths (9MA0) specification and written in Paper 1, Paper 2 and Paper 3 style. Every question includes a full worked solution and mark scheme, so you can see where marks are awarded rather than just whether you got the answer right.
